On 09/24, Joe Korty wrote:
Great. Thanks a lot for the report and discussion! And thanks
for your analysis (sent privately), the problem was completely
explained by you.
BTW, I forgot to show the test-case you sent me privately, perhaps
someone from CC might want to look... It really helped.
Oleg.
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/select.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
#define NUMSTOPS 10
int child_stopped = 0;
int waiting = 1;
void handler(int signo, siginfo_t *info, void *context)
{
if (info && info->si_code == CLD_STOPPED) {
printf("Child has been stopped\n");
waiting = 0;
child_stopped++;
}
}
int main(void)
{
pid_t pid;
struct sigaction act;
struct timeval tv;
act.sa_sigaction = handler;
act.sa_flags = SA_SIGINFO;
sigemptyset(&act.sa_mask);
sigaction(SIGCHLD, &act, 0);
setbuf(stdout, NULL);
printf("%d SIGSTOP/SIGCONT combinations to be sent.\n", NUMSTOPS);
if ((pid = fork()) == 0) {
/* child */
while(1) {
/* wait forever, or until we are
interrupted by a signal */
tv.tv_sec = 0;
tv.tv_usec = 0;
select(0, NULL, NULL, NULL, &tv);
}
return 0;
} else {
/* parent */
int s;
int i;
usleep(12000);
for (i = 0; i < NUMSTOPS; i++) {
waiting = 1;
printf("--> Sending SIGSTOP #%d\n", i);
kill(pid, SIGSTOP);
/*
Don't let the kernel optimize away queued
SIGSTOP/SIGCONT signals.
*/
while (waiting)
usleep(12000);
printf("--> Sending SIGCONT\n");
kill(pid, SIGCONT);
// usleep(12000);
}
/* POSIX specifies default action to be abnormal termination */
usleep(12000);
kill(pid, SIGKILL);
waitpid(pid, &s, 0);
}
if (child_stopped == NUMSTOPS) {
printf("Test PASSED\n");
return 0;
}
printf("Test FAILED\n");
return -1;
}
--
